/**
 * Copyright 2010-present Facebook.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.facebook;

import android.os.Handler;

import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * RequestBatch contains a list of Request objects that can be sent to Facebook in a single round-trip.
 */
public class RequestBatch extends AbstractList<Request>
{
  private static AtomicInteger idGenerator = new AtomicInteger();

  private Handler callbackHandler;
  private List<Request> requests = new ArrayList<Request>();
  private int timeoutInMilliseconds = 0;
  private final String id = Integer.valueOf(idGenerator.incrementAndGet()).toString();
  private List<Callback> callbacks = new ArrayList<Callback>();
  private String batchApplicationId;

  /**
   * Constructor. Creates an empty batch.
   */
  public RequestBatch()
  {
    this.requests = new ArrayList<Request>();
  }

  /**
   * Constructor.
   *
   * @param requests the requests to add to the batch
   */
  public RequestBatch(Collection<Request> requests)
  {
    this.requests = new ArrayList<Request>(requests);
  }

  /**
   * Constructor.
   *
   * @param requests the requests to add to the batch
   */
  public RequestBatch(Request... requests)
  {
    this.requests = Arrays.asList(requests);
  }

  /**
   * Constructor.
   *
   * @param requests the requests to add to the batch
   */
  public RequestBatch(RequestBatch requests)
  {
    this.requests = new ArrayList<Request>(requests);
    this.callbackHandler = requests.callbackHandler;
    this.timeoutInMilliseconds = requests.timeoutInMilliseconds;
    this.callbacks = new ArrayList<Callback>(requests.callbacks);
  }

  /**
   * Gets the timeout to wait for responses from the server before a timeout error occurs.
   *
   * @return the timeout, in milliseconds; 0 (the default) means do not timeout
   */
  public int getTimeout()
  {
    return timeoutInMilliseconds;
  }

  /**
   * Sets the timeout to wait for responses from the server before a timeout error occurs.
   *
   * @param timeoutInMilliseconds the timeout, in milliseconds; 0 means do not timeout
   */
  public void setTimeout(int timeoutInMilliseconds)
  {
    if (timeoutInMilliseconds < 0)
    {
      throw new IllegalArgumentException("Argument timeoutInMilliseconds must be >= 0.");
    }
    this.timeoutInMilliseconds = timeoutInMilliseconds;
  }

  /**
   * Adds a batch-level callback which will be called when the entire batch has finished executing.
   *
   * @param callback the callback
   */
  public void addCallback(Callback callback)
  {
    if (!callbacks.contains(callback))
    {
      callbacks.add(callback);
    }
  }

  /**
   * Removes a batch-level callback.
   *
   * @param callback the callback
   */
  public void removeCallback(Callback callback)
  {
    callbacks.remove(callback);
  }

  @Override
  public final boolean add(Request request)
  {
    return requests.add(request);
  }

  @Override
  public final void add(int location, Request request)
  {
    requests.add(location, request);
  }

  @Override
  public final void clear()
  {
    requests.clear();
  }

  @Override
  public final Request get(int i)
  {
    return requests.get(i);
  }

  @Override
  public final Request remove(int location)
  {
    return requests.remove(location);
  }

  @Override
  public final Request set(int location, Request request)
  {
    return requests.set(location, request);
  }

  @Override
  public final int size()
  {
    return requests.size();
  }

  final String getId()
  {
    return id;
  }

  final Handler getCallbackHandler()
  {
    return callbackHandler;
  }

  final void setCallbackHandler(Handler callbackHandler)
  {
    this.callbackHandler = callbackHandler;
  }

  final List<Request> getRequests()
  {
    return requests;
  }

  final List<Callback> getCallbacks()
  {
    return callbacks;
  }

  final String getBatchApplicationId()
  {
    return batchApplicationId;
  }

  final void setBatchApplicationId(String batchApplicationId)
  {
    this.batchApplicationId = batchApplicationId;
  }

  /**
   * Executes this batch on the current thread and returns the responses.
   * <p/>
   * This should only be used if you have transitioned off the UI thread.
   *
   * @return a list of Response objects representing the results of the requests; responses are returned in the same
   * order as the requests were specified.
   * @throws FacebookException        If there was an error in the protocol used to communicate with the service
   * @throws IllegalArgumentException if the passed in RequestBatch is empty
   * @throws NullPointerException     if the passed in RequestBatch or any of its contents are null
   */
  public final List<Response> executeAndWait()
  {
    return executeAndWaitImpl();
  }

  /**
   * Executes this batch asynchronously. This function will return immediately, and the batch will
   * be processed on a separate thread. In order to process results of a request, or determine
   * whether a request succeeded or failed, a callback must be specified (see
   * {@link Request#setCallback(com.facebook.Request.Callback)})
   * <p/>
   * This should only be called from the UI thread.
   *
   * @return a RequestAsyncTask that is executing the request
   * @throws IllegalArgumentException if this batch is empty
   * @throws NullPointerException     if any of the contents of this batch are null
   */
  public final RequestAsyncTask executeAsync()
  {
    return executeAsyncImpl();
  }

  /**
   * Specifies the interface that consumers of the RequestBatch class can implement in order to be notified when the
   * entire batch completes execution. It will be called after all per-Request callbacks are called.
   */
  public interface Callback
  {
    /**
     * The method that will be called when a batch completes.
     *
     * @param batch the RequestBatch containing the Requests which were executed
     */
    void onBatchCompleted(RequestBatch batch);
  }

  /**
   * Specifies the interface that consumers of the RequestBatch class can implement in order to be notified when the
   * batch makes progress. The frequency of the callbacks can be controlled using
   * {@link com.facebook.Settings#setOnProgressThreshold(long)}.
   */
  public interface OnProgressCallback extends Callback
  {
    /**
     * The method that will be called when a batch makes progress.
     *
     * @param batch   the RequestBatch containing the Requests which were executed
     * @param current the current value of the progress
     * @param max     the max (target) value of the progress
     */
    void onBatchProgress(RequestBatch batch, long current, long max);
  }

  List<Response> executeAndWaitImpl()
  {
    return Request.executeBatchAndWait(this);
  }

  RequestAsyncTask executeAsyncImpl()
  {
    return Request.executeBatchAsync(this);
  }
}
